diff --git a/site/graphql-js/APIReference-Execution.md b/site/graphql-js/APIReference-Execution.md
index 41b7e7e0fa..750c2889f8 100644
--- a/site/graphql-js/APIReference-Execution.md
+++ b/site/graphql-js/APIReference-Execution.md
@@ -38,7 +38,9 @@ export function execute(
   contextValue?: mixed,
   variableValues?: ?{[key: string]: mixed},
   operationName?: ?string
-): Promise<ExecutionResult>
+): MaybePromise<ExecutionResult>
+
+type MaybePromise<T> = Promise<T> | T;
 
 type ExecutionResult = {
   data: ?Object;